Many power systems have multiple generator sets for supplying electricity to electric power loads. Some such power systems may have a group of generator sets that can all connect in parallel with a bus and supply power to a bus. In some circumstances, such a power system may have all of the generator sets in the group shut down and disconnected from the bus with no electricity flowing in the bus. In other circumstances, it may be desirable to increase the number of active generator sets. In such circumstances, various events may warrant initiating the supply of electricity from one or more of the generator sets in the group to the bus. After one generator set is connected to the bus, the voltage, frequency, and phase angle of any additional generator sets connected to the live bus should match that of the bus. A closer match will result in a smoother transition and a lower level of shock to the generator sets and electric power load.
U.S. Pat. No. 4,492,874 issued to Near, on Jan. 8, 1985 (“the '874 patent”) discloses a power system with generator sets associated with an electrical power system, and a control method wherein the frequency and phase can be synchronized to the electrical power system in minimal time while minimizing thermal stress on the gas turbine hot-gas-path parts. The control method of the '874 patent is directed to synchronizing a gas turbine-driven generator to an AC power system by employing time control theory to directly drive the turbine-generator to a synchronization point. The fuel commands, synchronization points, and trajectories are selected in view of the need to minimize thermal stress on turbine hot-gas-path parts, while also minimizing time required for synchronization. The control method of the '874 patent uses two fuel commands, maximum fuel flow and minimum fuel flow, to drive the turbine-generator to a synchronization point. The minimum fuel flow command is issued for, at most, a predetermined maximum time duration calculated to minimize temperature stress on the gas turbine.
Although the control method of the '874 patent may allow phase and frequency matching in a minimal time while minimizing thermal stress on the gas turbine hot-gas-path parts, certain disadvantages persist. For example, the control method of the '874 patent uses actual data from the generator set, but then applies a model to calculate the speed adjustments. Using a model that has generator specific variables may be expensive to create, and the performance of the model will degrade as the gas turbine ages and its performance characteristics change. The '874 patent discloses that there are certain zones where the model will oscillate, without closing to a synchronization point, and then compensates by building in slight biases. There is a risk that the imperfections in the model over the actual gas turbine performance will offset the biases and lock the control method of the '874 patent in a loop where it cannot close the generator to a synchronization point that will allow the generator set to be connected to the live bus.
The power system and methods of the present disclosure are directed to one or more improvements in existing technology.